1. Field of the Invention
This invention relates generally to facsimiles or the like using a redundancy reduction encoding system and having vertical scan means, and more particularly to a vertical scan control method with a reduced number of stops of vertical scan.
2. Description of the Prior Art
As disclosed, for example, in Japanese Patent Laid-Open No. 17568/1981 entitled "Vertical Scan Method of Facsimile", laid-open on Feb. 19, 1981, one example of prior art technique divides in advance a vertical scan speed into N stages, reference values M.sub.1 and M.sub.2 are set in advance for a code buffer, acceleration, uniform speed and deceleration are selected in accordance with the number of the buffered code bits, and the vertical scan speed is changed one stage by one in the acceleration and deceleration ranges.
Accordingly, it is always necessary to manage the present vertical scan speed and the number of the buffered code bits.
When the number of the buffered code bits is near the reference values, it is necessary to frequently switch modes between acceleration and uniform speed, between uniform speed and deceleration or between acceleration and deceleration, and complicated vertical scan speed control has been necessary.
In a thermo-sensitive recording system, for example, which divides a recording head into a plurality of blocks and applies a current only to the blocks where black pixels exist, no consideration has been paid to the change of a power feed time for recording in the unit of scan lines in accordance with the content of a video signal to be recorded.